import java.util.HashMap;

/**
 * @author WHQ
 * @version 1.0
 * @date 2022-3-26 0026 下午 7:30
 */
public class Demo {
    public static void main(String[] args) {
        HashMap map=new HashMap(0);
        System.out.println(map.size());
        map.put("name","张三");
        System.out.println(map.get("name"));
        System.out.println(map.size());
    }
}
